A survey on the cadmium contamination in brown rice sold in Tokyo

全文

(1)33. Fundamental Toxicological Sciences (Fundam. Toxicol. Sci.) Vol.8, No.2, 33-36, 2021. Fundamental Toxicological Sciences URL : http://www.fundtoxicolsci.org/index_e.html. Data Report. A survey on the cadmium contamination in brown rice sold in Tokyo Yukino Segawa1, Setsuko Tabata1, Izumi Hirayama1, Kenji Iida1, Ikuko Matsuno1, Hisako Nakano1, Takeo Sasamoto1 and Toshiyuki Kaji2 Department of Food Chemistry, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan 2Deapartment of Environmental Health, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan 1. (Received March 30, 2021; Accepted March 31, 2021). ABSTRACT — Heavy metals are ubiquitous in the environment and nature, and even in trace amounts, chronic exposure to them can have negative health effects on humans. It is known that rice, in particular, easily accumulate cadmium (Cd). Cd can accumulate in the human body and affect human health. In Japan, rice is a staple food and a main leading source of Cd poisoning. The Tokyo Metropolitan Government has been investigating the Cd content in brown rice sold in Tokyo since 1973 in order to prevent Cd poisoning in humans. A survey result from 2010 to 2018 stated that there was no sample that exceeded the maximum limit (0.4 ppm). Moreover, compared with past survey reports in Tokyo, the Cd content in brown rice has obviously decreased. In this survey, cadmium intake from brown rice was not particularly problematic in terms of food hygiene. Key words: Cadmium, Brown rice, Food hygiene INTRODUCTION. Cadmium (Cd) is widely present in the environment, including soil, water, and various foods due to natural sources and industries (Bradl et al., 2005). Heavy metals, such as Cd, accumulate in the body when ingested over a long period of time. Even in trace amounts, it may affect human health. Cd causes diseases such as pneumonia, kidney damage, and osteomalacia (World Health Organization, 1992a, 1992b; Waalkes, 2003; Agency for Toxic Substance and Disease Registry, 2012). In Japan, the Itai-itai disease was caused by Cd contamination in the water and soil via the drainage of the mine in the Jinzu River basin in Toyama Prefecture (Tsuchiya, 1976; Aoshima, 2012, 2016). The inhabitants of this watershed ingested water. and rice containing Cd and developed osteomalacia. Rice is the largest source of dietary intake of Cd and it is estimated that about 40% of Cd dietary intake is taken from rice in Japan. Furthermore, it has been shown that rice absorbs Cd easily (Uraguchi et al., 2009). The Codex Alimentarius Commission of Food and Agriculture Organization/World Health Organization (FAO/WHO) has proposed the maximum limit of Cd concentration of 0.4 ppm (mg/kg) in polished rice grains (Codex Alimentarius, 2008). Following this, a safety criterion of 0.4 ppm has been set by the Ministry of Health, Labor, and Welfare for Cd concentration in polished grains of rice based on the Food Sanitation Law in Japan. The Tokyo Metropolitan Government has been investigating the content of Cd contained in brown rice sold in Tokyo since 1973 with the aim of preventing human. Correspondence: Yukino Segawa (E-mail: Yukino_Segawa@member.metro.tokyo.jp) Vol. 8 No. 2.

(2) 34 Y. Segawa et al.. Table 1. Cadmium concentration in brown rice by year (2010-2018). Level (ppm) Minimum Maximum 2010 185 91.4 n.d. 0.29 2011 181 96.2 n.d. 0.38 2012 186 90.3 n.d. 0.27 2013 183 80.3 n.d. 0.19 2014 180 81.7 n.d. 0.21 2015 180 71.1 n.d. 0.22 2016 180 72.2 n.d. 0.25 2017 169 77.1 n.d. 0.33 2018 186 80.1 n.d. 0.26 * n.d.: < 0.01 ppm *Cd concentrations less than the lowest LOD in samples was evaluated as a half of LOD. year. Number of samples. Number of positive (%). intake of Cd-contaminated rice in the city. In this study, we report the survey results of Cd content in brown rice during the nine years from 2010 to 2018 in Tokyo. MATERIALS AND METHODS Samples From 2010 to 2018, brown rice samples produced in various Japanese regions were collected from warehouses in Tokyo. Apparatus A microwave digestion system, Microwave (MultiWave3000, PerkinElmer, Inc., Waltham, MA, USA), was used for acid digestion. Determination of elemental concentration was carried out with graphite furnace atomic absorption spectrometry (GF-AAS, AA7000, Shimadzu Corporation, Kyoto, Japan). Reagents The reagents of analytical grade quality were used for all analyses. Water was purified using a Milli-Q system (Merck Millipore, Tokyo, Japan). The standard solution of 100 mg/L for Cd (chemical analysis grade) was obtained from Kanto Chemical (Tokyo, Japan). In the digestion and extraction procedures, the concentrated nitric acid (61%) and hydrogen peroxide (35%) were used that were obtained from Kanto Chemical. For GFAAS analysis, ammonium phosphate dibasic and ascorbic acid were used as the matrix modifier. Method The samples were homogenized using a food processor. About 0.5 g of each sample was accurately weighed, added with 8 mL of HNO3, and then left overnight. Next, 2 mL of hydrogen peroxide was added just before the Vol. 8 No. 2. Average value (ppm) 0.05 0.05 0.05 0.04 0.05 0.04 0.04 0.05 0.05. samples were microwave-digested. After being digested, the sample solution was made to cool down to room temperature, and it was made up to 50 mL with ultrapure water. Then, the Cd concentrations were determined by GF-AAS. The wavelength for Cd was set to 228.8 nm and the spectral bandpass to 0.5 nm. Then, for the matrix modifier, ammonium phosphate dibasic and ascorbic acid were used. In this method, the limit of quantitation (LOQ) for cadmium was 0.01 ppm. RESULTS AND DISCUSSION According to the result of 1630 samples from 2010 to 2018, no sample exceeded the maximum limit (0.4 ppm) that was mandated by the Food Sanitation Law in Japan. Over the 9 years, the average Cd concentration ranged from 0.04 to 0.05 ppm (Table 1). It should be noted that Cd concentrations that were less than the lowest LOQ in samples were evaluated as a half of the LOQ. According to previous reports (Hagiwara et al., 2010), between 1973 and 2009, the average of Cd content has been 0.04 to 0.09 ppm, and in some cases, brown rice that contained more than 0.4 ppm Cd were found every year from 1973 to 1981. However, since 1982, the number of brown rices containing more than 0.4 ppm of Cd has decreased significantly, and in the survey from 2002 to the present, no brown rice containing more than 0.4 ppm of Cd was found. The distribution of cadmium concentration in rice from 2010 to 2018 is shown in Fig. 1. Over the nine years, from 2010 to 2018, the ratio of Cd content below the limit of quantification (0.01 ppm) was 17.6%; between 0.01 ppm and 0.05 ppm, 42.4%; between 0.05 ppm and 0.1 ppm, 26.6%; between 0.1 ppm and 0.2 ppm, 11.9%; and between 0.2 and 0.4 ppm, 1.4%. Similar results were found in national surveys..

(3) 35 A survey on the cadmium contamination in brown rice in Tokyo. Fig. 1. Distribution of Cd concentration in brown rice from 2010 to 2018.. Table 2. Cadmium concentration in brown rice by production area. Number of samples Average value (ppm) Max value (ppm) < 0.01 0.01 ≤ x < 0.05 0.05 ≤ x < 0.1 0.1 ≤ x < 0.2 0.2 ≤ x < 0.4 > 0.4. Hokkaido 68 0.01 0.07 number (%) 38 55.9 28 41.2 2 2.9 0 0 0 0 0 0. Tohoku 745 0.05 0.33 number (%) 101 13.6 311 41.7 214 28.7 102 13.7 17 2.3 0 0. Kanto 312 0.04 0.22 number (%) 81 26.0 141 45.2 62 19.9 25 8.0 3 1.0 0 0. In the same span of years, the average value of Cd content was extremely lower than before 2009 (Hagiwara et al., 2010). This is thought to be an effect of the measures taken by the government and Ministry of Agriculture, Forestry and Fisheries to reduce Cd, for example, phytoextraction, soil dressing, and water management (Murakami et al., 2007; Arao et al., 2009). The Cd concentrations in brown rice are summarized in Table 2. They are classified into seven areas except for Okinawa and Shikoku. No significant difference was observed in the cadmium concentration between the areas. The average of cadmium concentration was ≤ 0.05 ppm in all regions, which is extremely low compared to the maximum limit. Samples with cadmium concentrations of 0.2-0.4 ppm were detected in four regions, namely Tohoku, Kanto, Chubu, and Kansai. The highest ratio of brown rice with low cadmium concentration was in Hokkaido. In conclusion, the cadmium concentration in brown rice was low in all regions and would unlikely to pose a risk to human health.. Chubu 444 0.05 0.38 number (%) 51 11.5 178 40.1 149 33.6 64 14.4 2 0.5 0 0. Kansai 20 0.05 0.23 number (%) 4 20.0 11 55.0 2 10.0 2 10.0 1 5.0 0 0. Chugoku 3 0.03 0.06 number (%) 0 0 2 66.7 1 33.3 0 0 0 0 0 0. Kyusyu 38 0.02 0.10 number (%) 13 34.2 24 63.2 0 0 1 2.6 0 0 0 0. Conflict of interest---- The authors declare that there is no conflict of interest. REFERENCES Aoshima, K. (2012): Itai-itai disease: cadmium-induced renal tubular osteomalacia − Current status and future perspective. Nippon Eiseigaku Zasshi, 67, 455-463. (in Japanese) Aoshima, K. (2016): Itai-itai disease: renal tubular osteomalacia induced by environmental exposure to cadmium — historical review and perspectives. Soil Sci. Plant Nutr., 62, 319-326. Agency for Toxic Substance and Disease Registry (ATSDR). (2012): Toxicological Profile for Cadmium 3.2.2.2 Health Effect- Renal effects. pp. 147-167, Atlanta. Arao, T., Kawasaki, A., Baba, K., Mori, S. and Matsumoto, S. (2009): Effects of water management on cadmium and arsenic accumulation and dimethylarsinic acid concentrations in Japanese rice. Environ. Sci. Technol., 43, 9361-9367. Bradl, H. (ed.) (2005): Heavy metals in the environment: origin, interaction and remediation, vol 6, pp.1-25, Elsevier, Amsterdam. Codex Alimentarius. (2008): Codex general standard for contaminants and toxins in foods and feed. Codex Stan, 193-1995. Hagiwara, T., Amemiya, T. and Yamanobe, H. (2010): Cadmium and Heavy Metal Contents of Brown Rice Carried in Tokyo. Ann. Rep. Tokyo Metr. Inst. Pub. Health, 61, 185-190. Vol. 8 No. 2.

(4) 36 Y. Segawa et al. (in Japanese) Murakami, M., Ae, N. and Ishikawa, S. (2007): Phytoextraction of cadmium by rice (Oryza sativa L.), soybean (Glycine max (L.) Merr.), and maize (Zea mays L.). Environ. Pollut., 145, 96-103. Tsuchiya, K. (1976): Epidemiological studies on cadmium in the environment in Japan: etiology of itai-itai disease. Fed. Proc., 35, 2412-2418. Uraguchi, S., Mori, S., Kuramata, M., Kawasaki, A., Arao, T. and Ishikawa, S. (2009): Root-to-shoot Cd translocation via the. Vol. 8 No. 2. xylem is the major process determining shoot and grain cadmium accumulation in rice. J. Exp. Bot., 60, 2677-2688. Waalkes, M. (2003): Cadmium carcinogenesis. Mutat. Res., 533, 107-120. World Health Organization. (1992a): Environ. Health Criteria 134. Cadmium. Geneva. World Health Organization. (1992b): Environ. Health Criteria 135. Cadmium − environmental aspects. Geneva..

(5)